(a) Field of the Invention
The present invention relates to a liquid crystal display, and more particularly to a liquid crystal display including a sensing unit for compensation driving.
(b) Description of the Related Art
Currently, flat panel displays, examples of which include organic light emitting diode displays (“OLED”), plasma display panels (“PDP”) and liquid crystal displays (“LCD”), are being actively developed as alternatives to heavy and large cathode ray tubes.
The PDP is a device that displays an image using plasma generated by a gas discharge, and the OLED display is a device that displays an image using electroluminescence of a specific organic material or a polymer. The LCD adjusts transmittance of light passing through a liquid crystal layer by applying an electric field to the liquid crystal layer, which is interposed between two display panels, and adjusting the intensity of the electric field, thereby obtaining a desired image.
In general, an LCD includes two display panels in which pixel electrodes and a common electrode are respectively provided, and a liquid crystal layer, which has a dielectric anisotropy, is interposed therebetween. The pixel electrodes are arranged in a matrix form and are connected to switching elements such as thin film transistors (“TFT”) to sequentially receive a data voltage row by row. The common electrode is formed over an entire surface of the display panel to receive a common voltage. A pixel electrode, the common electrode, and the liquid crystal layer therebetween constitute a liquid crystal capacitor, and the liquid crystal capacitor and a switching element that is connected thereto become a basic unit for constituting a pixel.
If an operating time period of the LCD is lengthened, a color bleach failure may be generated. The color bleach failure is a phenomenon in which a color that is represented by an input image signal is distorted to other colors. Users may interpret the phenomenon as a failure. For example, when a pixel that should be represented in a black color is represented by a gray color, a user may interpret such a representation as a failure of the LCD. When a switching element that transfers a data signal to a liquid crystal pixel is turned off a leakage current flows, whereby an undesired data signal is applied to the liquid crystal pixel and the phenomenon thus occurs. Specifically, switching elements of a plurality of liquid crystal pixels are connected to each of a plurality of gate electrodes extending from gate lines that are parallelly formed in a row direction. According to a selection signal that is sequentially applied to each of a plurality of gate electrodes on a gate line, if a switching element is turned on, a data signal is transferred to a liquid crystal layer through a data line. In this case, if a leakage current flows to a switching element that is turned off, a data signal to be applied to another liquid crystal pixel is applied to a liquid crystal pixel that is connected to the turned off switching element by the leakage current. Thereby, a color of the liquid crystal pixel that is connected to the switching element that is turned off is distorted.